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Discussion Starter #1
My 66 duetto alway runs great. I have been busy the last few months and haven't had it out in 2 weeks. It is a beautiful day here in SoCal so I thought I would drive it today. Unfortunately it won't start. I verified that I am getting fuel but I don't seem to be getting spark. When I measure across the coil I am only seeing around 7 volts. That seems low to me. I was always told that I should see 12v. It sounds like something has come lose or died? The motor cranks with authority and the battery reads 12v. Suggestions?

Thanks,

Ron
 

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First thing to check is the fuse box. Dirty contacts can cause such a drop.
Measure the voltage at each end of the ignition fuse. Or better yet, clean all of the fuse contacts and retry. A little dielectric grease on the fuse ends helps avoid some problems.
 

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there is a ballast resistor in line with the coil. normal voltage is around 6 or 7 volts with the ignition on and the points closed. there is a wire from the starter solenoid to the coil that jumps out this resstor for more voltage to start. the easiest check for whether the coil is working is to use a screwdriver to open the points with the high voltage lead near a ground. every time the points open, a hot blue spark should jump.
cliff
 

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Normally, a '66 Duetto with Bosch ignition doesn't have the ballast resistor. Later Marelli systems do, I believe.
 

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When I measure across the coil I am only seeing around 7 volts.
If indeed the measurement was across the coil, ie coil positive and coil negative, AND the points were closed, then 7 volts is the voltage drop through the coil primary. (never measured this I don't know if it's normal)
What is the voltage between coil positive and chassis ground?
 

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Discussion Starter #8
What is the voltage from the positive coil connection to ground with the key on ?
And the same reading when cranking ?
That you everyone for your replies and assistance. We did a sit down dinner at our home last night for 30 people so the wife has had me running around for the last 36 hours! I finally had a few minutes this morning to take a few more measurements with the DVM. Here is the situation.

12.25v exiting the fuse box checked to classis ground.

12.25 volts entering the coil checked to classis ground.

12.25 volts entering the coil checked by disconnecting the negative wire from the coil to the distributor and grounding the DVM to the distributor... i.e. removing the neg wire to the distributor.

7 volts across the coil measured with the neg lead connected to the distributor.

In other words I get a voltage drop when the negative side of the coil is connected to the distributor. I get 12v from the positive side of the coil to all other grounds including grounding directly to the distributor.

It sounds to me like there might be an issue with the coil. Does anyone have another thought before I go and by a new coil.

Thanks again,

Ron
 

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As mentioned in post 6, some voltage drop would be expected because of the primary coil resistance. Although I don't know the spec, the fact that current is going thru the coil with the points closed confirms coil primary continuity and continuity between the coil and distributor.
I'd look for a problem with the points.
 

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As mentioned, take the distr. cap off and see if the points are closed. If so , the voltage is right. Open the points and check the voltage across the coil.
Have you taken a spark plug wire out and hold it 1/4" from a ground and then cranked the motor ?
This will tell if there is a good spark or not.
 

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Discussion Starter #11
Points are closed. Cap rotor and points look good. Measured voltage across the coil while trying to start the car and it drops to 2.5v. I measured the resistance across the coil at 1.5 ohm and from the center to the + side at 9.8 ohm. I read that a good coil should be 1.6 ohm across and 13 ohm from the center to the + side.

I pulled a spark plug, grounded the threads and tried starting the car. No spark at all.
 

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Excellent !
I have a similar chart in an old manual and if followed will lead you to a working system.
Randomly replacing components is just chasing your tail.
 

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Cap off, rotor off, cranking the car and the points are not opening at all. Now what?
Usually the base plate will be adjustable to set the point gap. If it can done with a dwell meter that'd probably be more accurate.

Perhaps a photo of the distributor's innards/points/etc will help us see what we're dealing with?
 

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Discussion Starter #19
Here is a pic of the distributor innards. Do I just loosen the screw and reset the gap? What is the correct gap? Thanks again.

 

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yes, loosen the screw and with the cam lobe centered on the point arm, adjust to .016"
 
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